[Extensions] Don't allow built-in extensions code to be overridden

chrome/browser/extensions/extension_bindings_apitest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Contains holistic tests of the bindings infrastructure
 
 #include "chrome/browser/extensions/api/permissions/permissions_api.h"
 #include "chrome/browser/extensions/extension_apitest.h"
 #include "chrome/browser/net/url_request_mock_util.h"
 #include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/test/base/ui_test_utils.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/test/browser_test_utils.h"
 #include "extensions/browser/extension_host.h"
 #include "extensions/browser/process_manager.h"
 #include "extensions/test/extension_test_message_listener.h"
 #include "extensions/test/result_catcher.h"
+#include "net/test/embedded_test_server/embedded_test_server.h"
 
 namespace extensions {
 namespace {
 
 class ExtensionBindingsApiTest : public ExtensionApiTest {
  public:
   void SetUpOnMainThread() override {
     content::BrowserThread::PostTask(
         content::BrowserThread::IO, FROM_HERE,
         base::Bind(&chrome_browser_net::SetUrlRequestMocksEnabled, true));
@@ skipping 77 matching lines @@
 IN_PROC_BROWSER_TEST_F(ExtensionBindingsApiTest, ApiEnums) {
   ASSERT_TRUE(RunExtensionTest("bindings/api_enums")) << message_;
 };
 
 // Regression test for http://crbug.com/504011 - proper access checks on
 // getModuleSystem().
 IN_PROC_BROWSER_TEST_F(ExtensionBindingsApiTest, ModuleSystem) {
   ASSERT_TRUE(RunExtensionTest("bindings/module_system")) << message_;
 }
 
+IN_PROC_BROWSER_TEST_F(ExtensionBindingsApiTest, NoExportOverriding) {
+  ASSERT_TRUE(embedded_test_server()->InitializeAndWaitUntilReady());
+
+  // We need to create runtime bindings in the web page. An extension that's
+  // externally connectable will do that for us.
+  ASSERT_TRUE(LoadExtension(
+      test_data_dir_.AppendASCII("bindings")
+                    .AppendASCII("externally_connectable_everywhere")));
+
+  ui_test_utils::NavigateToURL(
+      browser(),
+      embedded_test_server()->GetURL(
+          "/extensions/api_test/bindings/override_exports.html"));
+
+  // See chrome/test/data/extensions/api_test/bindings/override_exports.html.
+  std::string result;
+  EXPECT_TRUE(content::ExecuteScriptAndExtractString(
+      browser()->tab_strip_model()->GetActiveWebContents(),
+      "window.domAutomationController.send("
+          "document.getElementById('status').textContent.trim());",
+      &result));
+  EXPECT_EQ("success", result);
+}
+
 }  // namespace
 }  // namespace extensions